JP2012050101A - Method and apparatus for scheduling in wireless communication network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide techniques to efficiently schedule and serve stations in a wireless network.SOLUTION: An access point may aggregate stations with flows carrying traffic having similar characteristics, e.g., VoIP flows. The access point may schedule these stations together in an overall service period. The access point may serve each station in a respective service period within the overall service period. The access point may send a multi poll frame at the start of the overall service period to indicate the start time and/or service period for each station. Each station may decide to power down until its start time. The service periods for the stations may overlap one another. The service period for each station may cover an initial transmission as well as additional transmission and/or retransmission.

Description

This patent application is filed on Jan. 10, 2006 as “WLAN AP SCHEDULER FOR WLAN AP SCHEDULER FOR maximizing power saving for S-APSD clients”. No. 60 / 758,076 entitled “MAXIMIZING POWER SAVE WITH S-APSD CLIENTS” and “S-APSD client (handset)” filed on January 18, 2006 Claiming priority to provisional application No. 60 / 759,730 entitled “WLAN AP SCHEDULER FOR MAXIMIZING POWER SAVE WITH S-APSD CLIENTS (HANDSETS)”. Is assigned to the assignee of the present application and is expressly incorporated herein by reference.

  The present disclosure relates generally to communication, and more specifically to techniques for scheduling transmissions and saving station power in a wireless communication network.

  Wireless networks are widely deployed to provide various communication services such as voice, video, packet data, and so on. These networks can support communication of multiple users by sharing available network resources. Examples of such networks include a wireless local area network (WLAN), a wireless personal area network (WPAN), and a wireless wide area network (WWAN). The terms “network” and “system” are often used interchangeably.

  A wireless network may include any number of access points and any number of terminals. The access point can serve as a coordinator for communication with the terminal. A terminal may be actively communicating with an access point, idle, or powered off at a given moment. Terminals may have different data requirements and performance. Thus, the main challenge is to schedule the terminals for transmission as efficiently as possible based on these requirements and performance and available network resources.

  Therefore, there is a need in the art for techniques for efficiently scheduling terminals in a wireless network.

  Techniques for efficiently scheduling and serving a station in a wireless network are described herein. A station may be a terminal and / or an access point. In one aspect, the access point aggregates flows that carry traffic with similar characteristics, eg, stations that have Voice over Internet Protocol (VoIP) flows. The access point schedules these stations together during the entire service period. The access point serves each station in each service period within the entire service period. Station aggregation, scheduling, and service provision will be described in detail later.

  In another aspect, power save multipole (PSMP) is used in combination with aggregation. The access point may send a PSMP frame at the start of the full service period. The PSMP frame can indicate the start time and / or service period of each station scheduled in the entire service period. Each station may receive a PSMP frame and decide to power down until its start time.

  In yet another aspect, stations are scheduled such that service periods overlap each other. The scheduled service period for each station may cover the initial transmission of the station and additional transmissions and / or retransmissions. The scheduled service period for the second serviced second station may overlap with the service period addition and retransmission portion of the first serviced first station. If no additional transmissions and / or retransmissions are required for the first station, the second station may be serviced at the start of the second station's scheduled service period immediately after the first station's initial transmission. Good.

  In yet another aspect, the access point blocks off specified periods of scheduled operations and notifies stations in the coverage area of these specified periods. The access point may then transmit at the start of the specified period without performing channel access.

  Various aspects and embodiments of the disclosure are described in detail below.

  The features and nature of the present invention will become apparent from the following detailed description, taken in conjunction with the drawings, in which like reference numerals are identified throughout.

1 shows a wireless network having one access point and a plurality of terminals. FIG. The figure which shows the transmission timeline of an access point. The figure which shows the operation | movement which is not scheduled. The figure which shows the scheduled operation | movement by individual service time. The figure which shows the scheduled operation | movement by aggregation. The figure which shows the scheduled operation | movement by aggregation. The figure which shows the operation | movement scheduled by aggregation and PSMP. The figure which shows the operation | movement scheduled by aggregation and PSMP. FIG. 5 shows a scheduled operation with duplicate service slots. FIG. 5 shows a scheduled operation with duplicate service slots. FIG. 5 shows a scheduled operation with duplicate service slots. The figure which shows the service slot by different staggering. FIG. 5 shows a scheduled operation with duplicate service slots and PSMP. FIG. 5 shows a scheduled operation with duplicate service slots and PSMP. FIG. 5 shows a scheduled operation with duplicate service slots and PSMP. The figure which shows the service slot given per transmission slot. FIG. 5 shows a scheduled operation with duplicate service slots. FIG. 5 shows a scheduled operation with duplicate service slots in a specified period. The figure which shows the scheduled operation | movement by PSMP in a designated period. FIG. 4 shows a process for scheduling stations by aggregation and serving them. The figure which shows the apparatus which schedules a station by aggregation and serves it. Diagram showing the process of scheduling by staggering and duplication. The figure which shows the apparatus scheduled by staggering and duplication. The figure which shows the process which operates a station. The figure which shows the apparatus for a station. The block diagram of an access point and a terminal.

Detailed description

  The term “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

  The scheduling techniques described herein may be used for various wireless networks such as WLAN, WPAN, WWAN, and so on. These techniques also include (1) a time division duplex (TDD) network in which data is transmitted on the downlink and uplink of a single frequency band at different time intervals, and (2) the downlink of the individual frequency band and It may be used for frequency division duplex (FDD) networks where data is transmitted on the uplink. For clarity, this scheduling technique is described below for a TDD WLAN.

  FIG. 1 shows a wireless network 100 having one access point 110 and a plurality of terminals 120a-120e. In general, a wireless network may include any number of access points and any number of terminals. An access point is a station that provides access to distribute services over a wireless medium to associated stations. The terms “wireless medium” and “channel” are used interchangeably herein. An access point, also referred to as a base station, base transceiver subsystem (BTS), Node B, and / or some other network entity, may include some or all of these functions. A terminal is a station that can communicate with another station via a wireless medium. A terminal can communicate with an access point or peer to peer with other terminals. A terminal may also be referred to as an access terminal, user terminal, mobile station, user equipment (UE), and / or some other entity, and may include some or all of these functions. A terminal may be a cellular phone, a handheld device, a wireless device, a personal digital assistant (PDA), a laptop computer, a wireless modem card, a cordless phone, and so on.

  In a centralized network, the network controller 130 couples to access points and coordinates and controls these access points. Network controller 130 may be a single network entity or a collection of network entities. In a distributed network, access points may communicate with each other as needed without using the network controller 130.

  The wireless network 100 can implement IEEE 802.11 series standards adopted by the Institute of Electrical and Electronics Engineers (IEEE). For example, the wireless network 100 may implement the existing IEEE 802.11 standards, IEEE 802.11, 802.11a, 802.11b, 802.11e, and / or 802.11g. Further, the wireless network 100 may implement IEEE 802.11n and / or 802.11s, which are the IEEE 802.11 standards under development. IEEE 802.11, 802.11a, 802.11b, 802.11g, and 802.11n cover different radio technologies and have different capabilities. IEEE 802.11e covers improving the quality of service (QoS) of the medium access control (MAC) layer. In IEEE 802.11e, a station that supports the QoS function is referred to as QSTA, and an access point that supports the QoS function is referred to as QAP. The QoS function refers to a mechanism used to provide parameterized and preferred QoS.

  A station (STA) may communicate with an access point (AP) for one or more flows. A flow is an upper layer (eg, TCP or UDP) data stream sent over a link. A flow may also be referred to as a data stream, a traffic stream, or the like. A flow can carry any type of data, such as voice, video, packet data, and the like. A flow may be used for a specific traffic class and may have specific requirements for data rate, latency or delay, and so on. The flow may be periodic or aperiodic. An aperiodic flow is a flow in which data is transmitted sporadically, for example, whenever data to be transmitted occurs. A periodic flow is a flow that transmits data at regular intervals. For example, a VoIP flow may send a data frame every 10 or 20 milliseconds (ms). As used herein, a frame may be a data frame, a null frame, a control frame, or some other type of frame. A frame may also be referred to as a packet, a data block, a data unit, a protocol data unit (PDU), a service data unit (SDU), a MAC PDU (MPDU), and so on. A call to a STA can have one or more arbitrary flows in one or more traffic types.

  FIG. 2 shows an exemplary transmission timeline 200 for the AP 110 in the wireless network 100. In general, each AP in a wireless network maintains a separate timeline for all transmissions covered by that AP. Next, the transmission timeline of the AP 110 will be described. The AP 110 periodically transmits beacons on the downlink. This beacon carries a preamble and an AP identifier (AP ID) that allows the STA to detect and identify the AP. The time interval between the start of two consecutive beacons is referred to as the target beacon transmission time (TBTT) or beacon interval. The beacon interval may be fixed or variable, and may be set to an appropriate period, for example 100 ms.

  A beacon interval may include any number of service periods for any number of STAs. A service cycle is a continuous period, during which the AP transmits one or more downlink frames to the STA and / or grants one or more transmission opportunities (TXOP) to the same STA. Can do. TXOP is a transmission time allocation on the link. The service period may or may not be scheduled. A given STA can have any number of service periods within a beacon interval.

  A service interval is a time interval between the start of two consecutive service periods for a given STA. The service interval for a periodic flow may be set based on the periodicity of traffic sent in that flow, eg 10 or 20 ms for VoIP, or some other value based on latency requirements. As shown in FIG. 2, different STAs may have different service intervals. Service time is the start of a service cycle. The service time for a given STA is a series of time instances separated by the service interval of that STA.

  IEEE 802.11e has two automatic power save delivery (APSD) modes called unscheduled ADSP (U-ADSP) and scheduled APSD (scheduled ADSP, S-ADSP). Is defined. An unscheduled APSD does not require centralized coordination. In this mode, each STA can independently select its service time. Scheduled APSD utilizes centralized scheduling of service times by the AP.

FIG. 3 shows the unscheduled APSD operation of one STA. STA selects the service time _{T 1.} In service time _{T 1,} STA executes the defined extended autonomous distributed channel access (EDCA) procedure by IEEE 802.11, accessing the wireless medium. Channel access takes an indefinite amount of time T _STA , which depends on whether the channel is busy and the EDCA access category (AC) used. Upon gaining access to the channel, the STA sends a trigger frame on the uplink (UL). This trigger frame may be a data frame (eg, a VoIP frame), a QoS null frame, or some other frame with an indication that it is a trigger frame. The frame formats for the various types of frames are described in the IEEE 802.11 document.

The AP may send an acknowledgment (Ack) on the downlink (DL) in response to receiving the trigger / data frame from the STA. In general, an AP may send an acknowledgment for a single data frame or a block acknowledgment for multiple data frames. Thus, “Ack” can be a single acknowledgment or any type of block acknowledgment. The AP may send data to the STA along with Ack, which is not shown in FIG. The response (Ack or data) is used by the STA to confirm the start of the service period. The STA remains awake in the service period until the service period is terminated by the AP or a beacon is received. If the AP is not ready for downlink data, the AP searches for data and performs channel access after sending an Ack confirming receipt of the trigger and the start of the service period, as shown in FIG. The data may be sent to the STA in subsequent downlink data frames. The STA may then send an Ack for the downlink data frame. As shown in FIG. 3, the AP may transmit a frame having an end-of-service-period (EOSP) bit set to “1” indicating the end of the service period of the STA. The STA continues to awake until the end of the unscheduled service period and acknowledges the data frame sent by the AP. In the example shown in FIG. 3, in an unscheduled service period, the STA is in the transmit state for two frames (one trigger / data frame and one Ack frame) and T _STA + T _AP +2 frames ( The period of (one Ack frame and one data frame) is in a reception state. For simplicity, in FIG. 3, all downlink frames have equal durations and all uplink frames also have equal durations. In general, a frame may have different durations, and the duration of each frame depends on the amount of data transmitted and the rate used for that frame.

FIG. 4 shows the scheduled APSD operation of two STAs with non-identical service times. AP schedules the service time _{T 1} of the STA1 and the STA2 of service time _{T 2.} In service time _{T 1,} AP accesses the wireless medium, and transmits the downlink data frame (eg, VoIP frame) to the STA1. The downlink data frame may include a poll that queries STA1 for any data to transmit and grants a TXOP for uplink transmission. The STA1 may transmit Ack for the downlink data frame, and may transmit data to the AP together with Ack. The AP then transmits an Ack for the uplink data frame from STA1. As shown in FIG. 4, the service cycle ends when the AP transmits a frame with the EOSP bit set to “1”. AP repeats the transmission procedure for STA2 in service time _{T 2.}

  The AP can estimate the duration of the service period of the STA based on various types of information. The rate at which data can be reliably exchanged between the AP and the STA may be estimated based on pilots and / or other transmissions. The amount of data to exchange can be known or predicted a priori in some applications (eg, VoIP). The service cycle period may be calculated based on the rate and amount of data to be exchanged. Also, the service period period may be determined based on a desired packet error rate and / or other factors.

  Scheduled APSD can provide a certain efficiency over unscheduled APSD. In scheduled APSD, the AP forwards data frames for the scheduled STA to the transmit buffer and is ready to transmit these data frames at service time. In contrast, an APSD service period that is not scheduled cannot be predicted by the AP because the timing and order of trigger frames from the STA cannot be predicted. Thus, buffer management is more complex with unscheduled APSD. The AP may not be able to prepare the data at SIFS time, and may need to retrieve the data, perform channel access, and send the data to the STA, as shown in FIG. In all cases, the AP responds to the trigger frame in SIFS (Short InterFrameSpacing). SIFS is equal to 16 microseconds (μs) for IEEE 802.11a / g and 10 μs for IEEE 802.11b.

  An AP can schedule a series of service times for any number of STAs with a scheduled APSD. The service time of each STA may be separated by the service interval of that STA, as shown in FIG. The AP may perform the transmission procedure for each STA at the service time for that STA. In the scheme shown in FIG. 4, the AP performs channel access for each STA. Multiple channel access for multiple STAs wastes time available for transmission. Furthermore, from the end of one scheduled service period to the start of the next scheduled service period, the channel may become overcrowded, which may delay service for one or more STAs.

  The STA can (1) power off all or part of the transmit chain during periods when the STA is not transmitting and / or (2) all or part of the receive chain during periods when the STA is not receiving. A power (or “sleep”) characteristic can be implemented. The power saving characteristics are particularly applicable to periodic flows such as VoIP, but can also be used for non-periodic flows. The power saving feature is beneficial for devices operating on handheld batteries (eg, cellular phones) because it reduces power consumption and extends the operating life between battery recharges.

  The scheduling techniques described herein support the power saving characteristics of STAs. This technique can be used for periodic and aperiodic flows. This technology can also be used for various wireless networks and standards. For clarity, this technique is described below for a VoIP flow with IEEE 802.11e scheduled APSD.

  In one aspect, the AP aggregates STAs with flows with similar characteristics and schedules these STAs together. For example, various types of traffic such as voice, video, packet data, etc. may be defined. Each traffic type may be associated with specific features and requirements such as minimum data rate, latency or delay. For example, voice may be associated with periodic transmissions and relatively severe delay requirements. The AP may aggregate STAs with the same traffic type flow, eg, VoIP. The AP may set a series of common service times for these STAs. Flow aggregation can simplify scheduling and buffer management and provide other benefits.

FIG. 5A illustrates one embodiment of scheduled APSD operation with aggregation of two STAs. The AP schedules the common service time T ₀ for both STA 1 and STA 2 and the full / aggregate service period. At service time T ₀ , the AP accesses the wireless medium and transmits a downlink data frame (eg, a VoIP frame) to STA 1. STA1 may send an Ack for the downlink data frame and send data to the AP along with Ack in response to a poll from the AP or after performing a channel access procedure. The AP then transmits Ack for the uplink data frame from STA1. The AP should set the EOSP bit to “1” in the downlink Ack frame to indicate that the service period of STA1 has ended. When the STA1 detects that the EOSP bit is set, the STA1 may enter the power saving mode.

  The AP may then send a downlink data frame to STA2. The STA2 may transmit Ack for the downlink data frame, and may transmit data to the AP together with Ack. The AP then transmits an Ack for the uplink data frame from STA2. The AP may set the EOSP bit in the downlink Ack frame to indicate that the STA2 service period has ended. When the STA2 detects that the EOSP bit is set, the STA2 may transition to the power saving mode.

FIG. 5B illustrates one embodiment of scheduled APSD operation with aggregation of two STAs and multi-frame transmission. The AP schedules a common service time T ₀ and a full service period for both STA1 and STA2. At service time T ₀ , the AP accesses the wireless medium and sends a first downlink data frame to STA 1. STA1 may transmit Ack and uplink data for the first downlink data frame. The AP may send a second downlink data frame to STA1 or retransmit the first downlink data frame. STA1 may transmit Ack for the first or second downlink data frame and uplink data. The AP may transmit an Ack for the uplink data frame from STA1. The AP may also set the EOSP bit in the downlink Ack frame to indicate that the STA1 service period has ended. When the STA1 detects that the EOSP bit is set, the STA1 may enter the power saving mode. The AP may then transmit to STA2 in a similar manner.

  An AP can serve aggregated STAs in various ways. In one embodiment shown in FIGS. 5A and 5B, the AP serves one STA brute-by-round, one STA at a time, fully services one STA, and then services the next STA. The AP may serve at STA1, then STA2, etc. In this embodiment, the service period for each STA is selected to be long enough to accommodate transmissions to and from the STA and possible retransmissions for data frames received in error. May be. The transmission for one STA and the retransmission, if any, are completed before starting the transmission for another STA.

  In another embodiment, the AP may make a round of STAs in the initial transmission and round the STAs in additional transmissions and / or retransmissions. The initial transmission of each STA may include a downlink data frame from the AP, an uplink data frame from the STA, and an Ack for the uplink data frame. The STA retransmission may be performed following the initial transmission of all STAs. In this embodiment, the total service period may be selected to be long enough to accommodate transmissions to and from all STAs and additional time for retransmissions.

  In both embodiments described above, the STA may transmit one uplink data frame in each service period under the assumption that the previous uplink data frame has been successfully transmitted. As shown in FIGS. 5A and 5B, the STA may piggyback the Ack for the previous downlink data frame and the current uplink data frame (eg, QoS data + CF-Ack frame).

  In scheduled APSD with aggregation, the AP performs a single channel access for all STAs aggregated together. This reduces channel access overhead and avoids scenarios where the channel is congested between scheduled service periods for STAs.

  In scheduled APSD by aggregation, the schedule for STAs can be conveyed in various ways. In one embodiment, the schedule for the STA is conveyed in a beacon. In this embodiment, the schedule may be updated at each beacon interval. In another embodiment, the flow schedule is determined and communicated when the flow is established. The schedule may be modified as necessary and communicated, for example, in frames transmitted during the service period.

In APSD scheduled by aggregation shown in FIGS. 5A and 5B, STA continues to awake from the common service time _{T 0.} When the STA can complete the transmission and reception of a frame or completes an authorized frame exchange based on certain rules, the STA may enter a power saving mode before the end of this service period. . In addition, the STA may enter the power saving mode upon receiving a frame in which the EOSP bit is set, or at the end of the scheduled service cycle of the STA.

In a scheduled APSD due to aggregation, the time that a STA remains awake depends on its own scheduled service period, which depends on the order in which the AP serves the STA during the entire service period. In FIG. 5A, each STA is in a transmitting state for one frame (one data frame with an Ack) and received in a period of T _AP +2 frames (one data frame and one Ack frame) + waiting time. Is in a state. T _AP is, AP is a time to access the wireless medium, varies with close to coming (impending) transmitted in the channel. The waiting time includes a service period for all STAs to be serviced first, and is about 50% of the total service period on average when the AP serves all STAs. Therefore, STAs that are serviced later have longer awake periods, whereas STAs that are serviced earlier have shorter awake periods. A STA may sleep as soon as it receives a downlink frame with the EOSP bit set or when the scheduled service period of that STA ends.

In another aspect, power save multi-pole (PSMP) is used in combination with scheduled APSD and aggregation to reduce the wake time of each STA and provide scheduling flexibility. PSMP is a multi-pole technology that enables efficient operation with scheduled APSD and aggregation. The AP selects a common service time T ₀ for all aggregated STAs. The AP transmits a PSMP frame, also called a multi-pole frame, at a common service time. The PSMP frame indicates the start time of each STA scheduled in the current full service period. Each STA may receive a PSMP frame and may decide to power down all or part of the receive chain until its start time based on the schedule indicated in the PSMP. This decision depends on various factors such as battery power available at the STA, time to start time, and so on. PSMP allows a STA to receive its transmission without necessarily being awake during the previous STA's service period. This improves the power savings of some STAs.

FIG. 6A illustrates one embodiment of scheduled APSD operation with PSMP for two STAs. The AP schedules a common service time T ₀ for both STA1 and STA2. At service time T ₀ , the AP accesses the wireless medium and sends a PSMP frame to the STA. The PSMP frame indicates that STA1 is serviced first, followed by STA2. STA2 may determine that it will be in a power saving state until its start time. The AP transmits a downlink data frame (for example, a VoIP frame) to STA1. The STA1 may transmit Ack for the downlink data frame, and may transmit data together with this Ack. The AP may then send an Ack for the uplink data frame and set the EOSP bit in the downlink Ack frame. STA1 may enter a power saving mode upon detecting that the EOSP bit is set or at the end of its service cycle. The AP may then transmit to STA2 in a similar manner.

  FIG. 6B illustrates one embodiment of scheduled APSD operation with PSMP and multi-frame transmission for two STAs. In the embodiment shown in FIG. 6B, the service period for each STA covers two downlink data frames, two uplink data frames, and an Ack frame, ie all five frames. The second downlink and uplink data frames may carry retransmissions or additional data for the first downlink and uplink data frames, respectively. The AP serves STA1 and STA2 in the manner described above for FIGS. 5B and 6A.

In scheduled APSD with aggregation and PSMP, the service period of each STA includes a PSMP period as well as transmissions for that STA. The service period of each STA is a part of the entire service period of all STAs. In the embodiment shown in FIG. 6A, each STA is in a transmit state for one frame (one data frame with an Ack) and T _AP +3 frames (one PSMP frame, one data frame, and one Ack frame). ) Is in a receiving state. A STA that is serviced later (eg, STA2 in FIGS. 6A and 6B) may be in a power saving state until the start time of that STA, and is approximately the same as the STA that is serviced earlier (STA1 in FIGS. 6A and 6B). It may be in the reception state for the time.

  The AP may schedule a plurality of all service periods continuously by PSMP. In one embodiment, the entire service period of the first PSMP may be used for downlink and / or uplink data frames and their Ack. The entire service period of the second PSMP immediately following or shortly after the first PSMP may be used for retransmission of data frames transmitted in the entire service period of the first PSMP. Each STA that does not require retransmission may be omitted from the entire service period of the second PSMP or may sleep.

  Some applications such as VoIP have stringent requirements on latency. If the service interval is relatively short (eg, 10 ms for VoIP), the AP completes transmissions for all STAs in the first round and then completes possible retransmissions for STAs within latency requirements in the second round It can be difficult to do. Thus, as shown in FIGS. 5B and 6B, each STA can meet this latency requirement by first completing the transmission and retransmission of one STA before serving the next STA. However, if the AP allocates two downlink data frames and two uplink data frames per STA to allow retransmission, as shown in FIGS. 5B and 6B, the later served STA will be more Awake for a long period. Furthermore, if there is no need for retransmission for a given STA, there is a gap in the entire service period and this unused medium time can be wasted.

  In yet another aspect, overlapping scheduling is used to efficiently utilize the time available for transmission, allowing STAs to meet stringent latency requirements, and helping STAs save power. In one embodiment, for example, at the start of a wireless network or when one or more flows of a given traffic type (eg, VoIP) are established, the AP determines the total service period of the STA. The AP divides the entire service period into service slots. Service slots may also be referred to in other terms. Service slots are defined to overlap each other. The duration of the entire service period, the number of service slots, the duration of each service slot, and the amount of service slot overlap, for example, the number of scheduled STAs, the amount of data for each STA, the estimated link data rate sustained in a given STA , Desired residual packet error rate (after retransmission), desired maximum delay range for MAC SDU, and so on.

  In one embodiment, the duration of each service slot is set to approximately twice the time to transmit a nominal data frame at its nominal rate and the time to transmit its Ack on each of the downlink and uplink. A nominal data frame is an average size frame of a particular traffic type and may be 180 bytes for VoIP. The nominal rate is the rate that is considered certain for a given link and can be determined based on signal quality measurements and link adaptation tables. The first half of the service slot may be used to transmit data frames on each link, and the second half of the service slot may be used to send additional frames or retransmissions on each link. The service slot may be defined such that the second half of the service slot overlaps the first half of the subsequent service slot. The AP may assign service slots of all service periods to STAs, for example, in order of arrival. The AP serves each STA within its assigned service slot.

FIG. 7A illustrates one embodiment of scheduled APSD operation with overlapping service slots of three STAs. In the embodiment shown in FIG. 7A, each service slot covers two downlink data frames, two uplink data frames, and an acknowledgment, ie, all five frames. Service slot 1 starts from a common service time T _0. Service slot 2 starts at time _{T 2,} which are _{T OS2} minutes offset from service time _{T 0.} T _OS2 is the time to transmit one downlink data frame, one uplink data frame, and one Ack frame for STA1. T _OS2 may be the minimum time to service STA1. Service slot 3 starts from the time _{T 3,} which are _{T OS3} minutes offset from service time _{T 0.} T _OS3 is equal to the time to transmit T _OS2 and one downlink data frame, one uplink data frame, and one Ack frame for STA2. T _OS3 may be the minimum time to service STA1 and STA2. The AP assigns service slot 1 to STA1, service slot 2 to STA2, and service slot 3 to STA3. The entire service period covers service slots 1, 2 and 3 of three STAs.

FIG. 7B shows transmission of one downlink data frame to each of the three STAs using the service slot shown in FIG. 7A. At the service time T ₀ , the AP accesses the wireless medium. In the first half of service slot 1, the AP sends a first downlink data frame to STA1, STA1 sends an uplink data frame with an Ack for the downlink data frame, and the AP sends an Ack for the uplink data frame. . In this example, the AP has no more data for STA1, and sets the EOSP bit in the downlink Ack frame. When the STA1 detects that the EOSP bit is set, the STA1 may enter the power saving mode. The AP may then serve STA2 in a manner similar to STA1. In this example, the AP transmits a downlink data frame to STA2, receives an uplink data frame together with Ack from STA2, and transmits an Ack frame in which the EOSP bit is set. The AP may then serve STA3 in a manner similar to STA1 and STA2.

  FIG. 7C shows transmission of two downlink data frames to STA1 using the service slot shown in FIG. 7A. In this example, the AP transmits a first downlink data frame to STA1, receives a first uplink data frame from STA1, and transmits a second downlink data frame or first downlink. A data frame is retransmitted to STA1, a second uplink data frame or a retransmission of the first uplink data frame is received from STA1, and an Ack for the first or second uplink data frame is transmitted. After serving STA1, the AP serves STA2, transmits a downlink data frame to STA2, receives an uplink data frame from STA2, and transmits an Ack for the uplink data frame. The AP then services STA3 in a manner similar to STA2.

  FIGS. 7B and 7C illustrate two exemplary scenarios where data can be exchanged between the AP and STA during the service slot shown in FIG. 7A. The data may be exchanged in other ways depending on the amount of data to be transmitted and the transmission result. For example, the AP may send two downlink data frames to STA2 or STA3 instead of STA1.

  In the embodiment shown in FIG. 7A, each service slot covers two downlink data frames and two uplink data frames, and the second downlink frame and uplink frame are used for additional data or retransmission. The APs and STAs typically transmit at nominal rates that are considered reliable on these links. Therefore, it is unlikely that frames will usually be lost due to collisions, out of range, or other conditions for each STA. In a possible scenario, there is no need for retransmission for a STA, the second half of the service slot for that STA is not used, and the AP can service the next STA early. However, if a STA's frame is lost, the second half of the STA's service slot may be used immediately for retransmission. Thus, duplicate service slots help reduce retransmissions whenever needed, while potentially reducing the awake time of later serviced STAs.

With overlapping service slots, each STA may be awake during all or part of its service slot. The start of each service slot may be given with reference to a common service time T ₀ as shown in FIG. 7A. Each STA may be awake from the start of the service slot. The actual service period for each STA may be part of a service slot, for example as shown in FIGS. 7B and 7C.

  FIG. 7A shows that each service slot covers five frames (two downlink data frames, two uplink data frames, and one Ack frame), and each service slot is the same as the previous service slot and two frames. Fig. 4 illustrates an overlapping scheduling embodiment. In this embodiment, each STA typically has one downlink data frame and one uplink data frame in each service period, and the second downlink data frame and uplink data frame are additional data and / or retransmissions. It may be used for applications (eg, VoIP) used for.

  FIG. 8 shows another scheduling embodiment where each service slot covers five frames, but overlaps the previous service slot by three frames (rather than two frames). This embodiment may be used in applications where each STA typically has one downlink data frame in each service period. Other frames in the service slot may be used for additional data and / or retransmission.

  In general, service slots may be defined with equal or different durations, and each service slot may have any duration. The service slot for each STA is selected based on data requirements, expected payload on the downlink and uplink in each service period, estimated link data rate from AP to STA and STA to AP, and / or other factors. May be. Also, the actual service slot period of each STA may be selected based on the possibility of additional transmission and retransmission of the previously scheduled STA. The actual start time of a given STA depends on the time at which the AP completes service for the previous STA. The actual start time of a later serviced STA is typically more variable than the actual start time of a previously serviced STA. Thus, the service slots of later STAs may be extended to compensate for larger variations in the actual start times of these STAs.

  In general, service slots may overlap each other by equal or different amounts, and each service slot may overlap any amount with another service slot. The amount of overlap may be selected based on the frame error rate (which affects retransmission), the likelihood and amount of additional data to transmit, the amount of actual start time variation, and so on. For example, as shown in FIGS. 7A and 8, the same amount of overlap may be used for all STAs. Instead, different amounts of overlap may be used for different STAs. For example, more overlap may be used for later STAs to compensate for larger variations in actual start times.

  In one embodiment, the service slot is defined based on the minimum amount of data that is sent to each STA during the service period. When a minimum amount consisting of one downlink data frame and one uplink data frame is sent for each STA, the start of the service slot may be defined as shown in FIG. 7A. When a minimum amount of one downlink data frame is sent for each STA, the start of the service slot may be defined as shown in FIG. This embodiment ensures that each STA is awake at the earliest time that data can be sent to that STA.

  A service slot may be defined long enough to ensure that each STA remains awake during its transmission. As soon as the EOSP bit is set, each STA may go to sleep and does not have to be awake for the entire service slot period, so lengthening the service slot does not significantly affect power savings.

  7A to 8 show service slots in one service interval. The service slot may be repeated during each service interval, which may be for example 10 or 20 ms for VoIP. The AP can service multiple scheduled STAs during each beacon interval.

  The schedule by service slot can be formed and / or updated in various ways. In one embodiment, once a flow is established, the flow is assigned an appropriate service slot, and the assigned service slot does not change throughout the duration of the flow. When the flow ends, the service slot assigned to the flow becomes open and may be assigned to another flow. In another embodiment, the schedule may be updated as flows are added or dropped. In this embodiment, the active flow may be assigned a new service slot to reduce unused gaps between assigned service slots. Typically, each STA's service slot may be communicated in a beacon, in a frame sent to the STA, and / or during flow establishment by the TSPEC (11e) procedure. Schedule changes and updates may be communicated in beacons or frames sent to the STA.

  Duplicate service slots may be used with PSMP. With PSMP, service slots can be updated during each service interval, which can improve power savings.

  FIG. 9A illustrates one embodiment of scheduled APSD operation using overlapping service slots and PSMP for three STAs. In the embodiment shown in FIG. 9A, each service slot assigned PSMP covers two downlink data frames, two uplink data frames, and a total of five acknowledgment frames. Further, each service slot covers a PSMP frame. Service slots overlap each other as described above in FIG. 7A. The AP assigns service slot 1 to STA1, service slot 2 to STA2, and service slot 3 to STA3.

FIG. 9B shows an exemplary transmission for three STAs with overlapping service slots and PSMP. At the service time T ₀ , the AP accesses the wireless medium and transmits a PSMP frame to the STA. The PSMP frame carries a service slot assigned to the STA. All three STAs receive PSMP frames and determine their service slots. STA2 and STA3 may be determined to be a power-saving state until the start time _{T 2} and _{T 3,} respectively, which are shown in Figure 9A. The AP serves STA1, then STA2, and then STA3 as described above for FIG. 7B. When each STA detects that the EOSP bit is set, it may enter a power saving mode before the end of the service slot.

  FIG. 9C shows the service slots of STA1 and STA3 after the call to STA2 is completed. In the embodiment shown in FIG. 9C, the AP assigns service slot 1 to STA1 and service slot 2 to STA3. As shown in FIG. 9C, when STA2 completes the call, the AP may change the service slot and start time of STA3 where the call is still in progress. If STA1, not STA2, completes the call, the AP may assign service slot 1 to STA2 and service slot 2 to STA3.

  In general, PSMP allows the AP to flexibly update the STA schedule during each service interval. Each time the flow ends or the STA completes the call, the AP may reconfigure the schedule for the next service interval. This flexible scheduling allows the AP to efficiently manage resources and remove unused holes in the schedule.

In overlapping service slots with PSMP, each STA may be awake in all or part of T _PSMP and the rest of the service slot. T _PSMP includes the channel access delay of the AP and the duration of the PSMP frame. The STA knows the service time T ₀ of the PSMP frame during each service interval and may wake up to receive the PSMP frame. The STA may obtain the service slot from the PSMP frame and go to sleep until the start of the service slot.

  In another embodiment of overlapping service slots, the AP determines the total service period of the STA and divides the entire service period into non-overlapping transmission slots. A transmission slot may also be referred to in other terms. Each transmission slot may cover one or more downlink frames and one or more uplink frames. The duration of the total service period, the number of transmission slots, and the duration of each transmission slot may be selected based on various factors such as the number of scheduled STAs, the amount of data for each STA, and the like.

  In one embodiment, the duration of each transmission slot is approximately set to the time to transmit a nominal data frame (eg, 60 to 180 bytes for VoIP) at a nominal rate on one link. In another embodiment, the duration of each transmission slot is approximately set to the time to transmit a nominal data frame at the nominal rate in each of the downlink and uplink. In yet another embodiment, the duration of each transmission slot is approximately set to the time to transmit a nominal data frame at a predetermined rate (eg, 24 Mbps). In yet another embodiment, the duration of each transmission slot is set to a fixed duration, eg, 500 μs, 1 ms, or other duration.

  The transmission slots during the entire service period may be numbered sequentially, eg 1, 2, 3, etc. Each STA may be assigned a sufficient number of transmission slots to cover the expected transmissions and retransmissions for that STA during the service interval. A given transmission slot may be assigned to multiple STAs.

  FIG. 10 illustrates one embodiment of scheduled APSD operation with overlapping service slots given per transmission slot. In the embodiment shown in FIG. 10, each transmission slot (transmission slot, trans slot) is used to transmit one frame on one link. Each STA is assigned five transmission slots that can be used to transmit two downlink data frames, two uplink data frames, and an Ack frame. STA1 is assigned transmission slots 1 to 5, STA2 is assigned transmission slots 4 to 8, and STA3 is assigned transmission slots 7 to 11. Each STA's scheduled service period or service slot is formed by all transmission slots assigned to that STA. The scheduled service periods for STA1 and STA2 overlap in transmission slots 4 and 5. The scheduled service periods for STA2 and STA3 overlap in transmission slots 7 and 8. An AP can serve that STA using any transmission slot assigned to each STA.

  In general, a transmission slot may be defined with any duration. Further, a given STA may be assigned any number of transmission slots, and any of the available transmission slots may be assigned. STAs scheduled adjacent to each other can share any number of transmission slots. The transmission slot structure can simplify the signaling that conveys the scheduled service period of each STA. For example, the scheduled service period may be conveyed by (1) the first and last assigned transmission slots, (2) the first transmission slot and the number of transmission slots, or (3) some other manner.

FIG. 11 illustrates another embodiment of scheduled APSD operation with overlapping service slots of three STAs. In the embodiment shown in FIG. 11, each service slot starts at a specific start time and ends at the end of the full service period or possibly earlier. Service slot 1 starts at common service time T ₀ , service slot 2 starts at T ₂ offset from T ₀ by T _OS2 , and service slot 3 starts at T ₃ offset from T ₀ by T _OS3. . T _OS2 may be the minimum time to service STA1, and T _OS3 may be the minimum time to service STA1 and STA2. The AP assigns service slot 1 to STA1, service slot 2 to STA2, and service slot 3 to STA3.

  In the embodiment shown in FIG. 11, each STA monitors transmissions to that STA from the start time. Each STA can exchange any number of frames with the AP. Each STA may enter a power saving mode upon detection of a set EOSP bit, at the end of a scheduled service period, or at the end of an entire service period. In the embodiment of FIG. 11, any number of additional transmissions and retransmissions can be made to the STA.

In the above embodiment, the AP performs channel access every full service period before transmission on the downlink. The channel access period varies and depends on the activity in the channel. Each STA is awake during the channel access by the AP. The AP is prioritized to access the channel, and can obtain access to the channel after waiting for a shorter time (PIFS time) than the STA. However, the channel access delay _TAP depends on the current traffic conditions of the channel and the time required to complete an ongoing transmission. If there is traffic in the channel, it will be difficult to predict when an ongoing transmission will be completed. If the ongoing transmission is a multiple frame transmission separated by SIFS time, the AP needs to wait until the frame exchange sequence is complete before it can access the channel. Fluctuating channel access delays determine when APs can perform STA's scheduled APSD operations, which affects the power savings of these STAs.

The AP may limit the maximum transmission by the STA in order to limit the worst case channel access delay T _AP . IEEE 802.11e defines a QoS procedure that allows a TXOP to be defined for each access class for contention-based traffic. Four access classes are defined for voice, video, best effort, and background. A TXOP limit of “0” for a given access class indicates that the STA can transmit only one data frame per channel access for that access class. The AP may set the TXOP limit for each of the four access classes to “0”. This setting reduces the worst case channel access delay of the AP to the time required to transmit the maximum size packet (usually 1500 bytes) at the average rate + SIFS time + time required for the next Ack + PIFS time. At an average rate of 24 Mbps, the worst case channel access delay for a single STA accessing at the same time can be less than 700 μs for every service interval.

  In yet another aspect, the AP blocks off specified time periods of scheduled APSD operations and notifies these specified periods to STAs in the coverage area. A designated period may be used for one or more total service periods of one or more traffic types. The designated periods may be separated by the service interval of the STAs serviced in these designated periods. The AP may send signaling on the beacon to inform the STA of the specified period within the beacon interval and / or set the specified period in other ways including CTS (CTS-to-self) transmission for itself. You may tell. By informing the STA of the specified periods, the AP can reasonably ensure that the channel is clear during these periods. Therefore, the AP may transmit data at the start of the specified period without having to perform channel access.

FIG. 12 illustrates one embodiment of scheduled APSD operation with overlapping service slots in a specified period of three STAs. In the embodiment shown in FIG. 12, the specified period begins at T _0, the T ₀ is used as a common service time of three STA. The specified period is divided into three overlapping service slots. Each service slot covers a total of five frames: two downlink data frames, two uplink data frames, and an Ack frame. Service slot 1 starts at T ₀ , service slot 2 starts at T ₂ from T ₀ to T _OS2 , and service slot 3 starts at T ₃ from T ₀ to T _OS3 . T _OS2 may be the minimum time to service STA1, and T _OS3 may be the minimum time to service STA1 and STA2. The AP assigns service slot 1 to STA1, service slot 2 to STA2, and service slot 3 to STA3. The AP, a first downlink data frame by the service time T ₀ without performing channel access may be transmitted to the STA1. STA2 and STA3 may sleep until _{T 2} and _{T 3} respectively start time.

FIG. 13 shows an embodiment of a scheduled APSD operation with overlapping service slots and PSMP in a specified period of three STAs. In the embodiment shown in FIG. 13, the specified period starts at T ₀ and is divided into three overlapping service slots. In this embodiment, the AP may send a PSMP frame at service time T ₀ without having to perform channel access. Each STA may receive a PSMP frame at T ₀ , determine the start time of the STA, and determine whether to sleep until that start time.

In the embodiment shown in FIGS. 12 and 13, the AP and STA know the designated period in advance and reserve the channel by any one of the above techniques. Therefore, the AP may transmit immediately without performing channel access. Furthermore, STA knows ensuring initiation time, during the channel access period T _AP varying need not be awake, may sleep longer. Note that the service time of the previous STA varies.

  For all of the above scheduling embodiments, the STA may have a variety of STA power, battery-powered STA usable power, STA link quality, amount of data exchanged with the STA, billing, etc. Schedules may be scheduled in an order determined based on factors. In one embodiment, STAs with lower power performance may be scheduled first or first, and STAs with higher power performance (eg, AC powered STAs) may be scheduled last or later. Power may be quantified by total battery capacity or remaining battery capacity. In another embodiment, a STA with a high quality link (eg, a STA located near an AP) may be scheduled first or earlier because the service time of this STA does not vary much. STAs with poor link quality or uncertain links may be scheduled later. In yet another embodiment, the order of schedules may be determined based on service costs, for example, STAs that pay more for services may be scheduled first, saving more power.

  FIG. 14 illustrates one embodiment of a process 1400 for scheduling and servicing stations by aggregation. Process 1400 may be performed by an access point. At least two stations with a particular traffic type (eg, VoIP) are aggregated and scheduled for the entire service period (block 1412). The total service period includes the service period of each station. Station service periods may be staggered and / or overlapped. The station's service cycle may begin at the beginning of the full service cycle (eg, as shown in FIG. 5A), or it may be staggered at different times (eg, as shown in FIGS. 6A, 7A, and 9A). You may start. The station service period may end at different times (eg, as shown in FIGS. 5A and 7A). Station service cycles may overlap in the data portion (eg, as shown in FIGS. 5A and 7A) or may not overlap in the data portion (eg, as shown in FIGS. 6A and 9A). . The entire service period may be repeated at predetermined intervals. Signaling may be transmitted (eg, in beacons, PSMP frames, data frames, etc.) to convey the service period of the station (block 1414).

  Each station is served in that station's service cycle within the entire service cycle (block 1416). Typically, any number of data frames can be transmitted to the station on the downlink and any number of data frames can be received from the station on the uplink during the service period. Signaling may be sent to the station to indicate the end of the service period (block 1418). Alternatively or additionally, the service period may end at a specified time.

  FIG. 15 shows an embodiment of an apparatus 1500 that schedules stations by aggregation and serves them. Apparatus 1500 aggregates at least two stations having a particular traffic type (eg, VoIP) and schedules them for the entire service period (block 1512) and signaling to convey the station's service period (eg, beacon, Means for sending (in a PSMP frame, etc.) (block 1514), means for servicing each station in its service cycle within the entire service period (block 1516), and signaling indicating the end of the station's service period to each station Means (block 1518) for sending (e.g., EOSP bits).

  FIG. 16 illustrates one embodiment of a process 1600 for scheduling and servicing stations by staggering and duplication. Process 1600 may be performed by an access point. The first station is scheduled with a first period having a first time period, a first start time, and a first end time (block 1612). The second station is scheduled with a second period having a second period, a second start time prior to the first end time, and a second end time (block 1614). The third station may be scheduled with a third period having a third period, a third start time prior to the second end time, and a third end time (block 1616). The first, second, and third end times may be different times (eg, as shown in FIG. 7A) or the same time (eg, at the end of the entire service period). The first, second and third periods are staggered and overlap each other. The first, second, and third periods may be, for example, three overlapping service slots, as shown in FIG. 7A or 9A.

  The first, second, and third time periods may be selected based on predicted data payload, data requirements, frame error rate, and the like. The first, second, and third periods may cover the same number of data frames (eg, two data frames on each link). The first, second, and third periods may have the same period or different periods. The first period may include a first portion of the initial transmission of the first station and a second portion of the additional transmission and / or retransmission of the first station. The second start time may be at the end of the first portion of the first period. Further, the second start time may be approximately halfway between the first start time and the first end time. The first, second, and third periods may be repeated at predetermined intervals, which may be in the range of 10-20 ms, for example for VoIP.

  The first, second, and third periods and predetermined intervals may be conveyed in beacons, in multi-pole frames (PSMP frames), during call or link establishment, in data frames, and so on. The first, second, and third periods may be constant during the call or may be updated during the call.

  The first transmission is sent to the first station during the first period (block 1622). Channel access may be performed before the first transmission if necessary, or may be omitted if the entire service period is blocked off. An indication of the completion of the first transmission (eg, the EOSP bit) is potentially transmitted to the first station prior to the end of the first period (block 1624). The second transmission is sent to the second station during the second period, potentially before the end of the first period (block 1626). An indication of the completion of the second transmission is sent to the second station, potentially before the end of the second period (block 1628). The third transmission is sent to the third station during the third period, potentially before the end of the second period (block 1630). Each transmission may be one or more data frames on the downlink and / or one or more data frames on the uplink. Each transmission may also include data that is retransmitted due to frame loss. The data frame may be VoIP and / or some other type of traffic.

  FIG. 17 shows an embodiment of an apparatus 1700 for scheduling stations by staggering and duplication. Apparatus 1700 includes means for scheduling a first station in a first period having a first period, a first start time, and a first end time (block 1712), a second period, Means for scheduling the second station in a second period having a second start time prior to the first end time and a second end time (block 1714); a third period; Means for scheduling a third station in a third period having a third start time and a third end time prior to the end time (block 1716), and the first station during the first period Means for sending a first transmission to the first station (block 1722) and means for sending an indication of completion of the first transmission (eg EOSP bit) to the first station, potentially before the end of the first period. ( Lock 1724), means for sending a second transmission to the second station during the second period, and possibly before the end of the first period (block 1726), and the completion of the second transmission Means for sending an indication to the second station, potentially before the end of the second period (block 1728), and a third period, possibly before the end of the second period, Means for sending a third transmission to the station (block 1730).

  FIG. 18 illustrates one embodiment of a process 1800 for operating a station, eg, a terminal. The station receives signaling in a first period that the station can receive transmissions (block 1812). The first period overlaps with a second period in which another station can receive the transmission. The first period may be repeated at a predetermined interval. Signaling may be received by multi-pol (PSMP) frames, beacons, frames sent during call establishment, frames sent during previous service periods, and so on. If signaling is received before the first period (eg, in a multi-pole frame), the station will power off the receive chain based on the length of time from the reception of the signaling to the start of the first period. May be determined (block 1814).

  The station monitors transmissions sent to the station during the first period, eg, from the beginning of the first period (block 1816). The station may receive transmissions of one or more data frames on the downlink and / or may transmit one or more data frames on the uplink during the first period (block 1818). . Upon receiving an indication of completion of transmission to the station, eg, an EOSP bit, the station may transition to a power saving mode before the end of the first period (block 1820).

  FIG. 19 shows an embodiment of an apparatus 1900 for a station. Apparatus 1900 provides means for receiving signaling in a first period in which a station can receive transmissions, and in a first period that overlaps a second period in which another station can receive transmissions. (Block 1912) and means (block 1914) for determining whether to power-down the receiving chain based on the time length from the reception of signaling to the start of the first period, during the first period, for example, Means for monitoring transmissions sent to the station from the beginning of the first period (block 1916), and during the first period, the transmission of one or more data frames on the downlink and / or up Means for transmitting one or more data frames on the link (block 1918) and an indication of completion of transmission to the station, eg EOSP bit Upon receipt, and means (block 1920) to remain in the power-saving mode before completion of the first cycle.

  FIG. 20 shows a block diagram of an access point 110 and a terminal 120x that may be one of the terminals of FIG. On the downlink, at the access point 110, a transmit (TX) data processor 2012 receives traffic data from the data source 2010, control data (eg, Ack) from the controller / processor 2020 for the terminal scheduled for transmission, and Scheduling information is received from the scheduler 2024. TX data processor 2012 processes (eg, encodes, interleaves, modulates, and scrambles) each terminal's data based on the rate selected for that terminal, processes control data and scheduling information, and generates data chips To do. A transmitter (TMTR) 2014 processes (eg, analog converts, amplifies, filters, and frequency upconverts) the data chips and generates a downlink signal that is transmitted from antenna 2016 to the terminal.

  In terminal 120x, antenna 2052 receives the downlink signal from access point 110 and provides the received signal. A receiver (RCVR) 2054 processes the received signal and provides samples. A receive (RX) data processor 2056 processes (eg, descrambles, demodulates, deinterleaves, and decodes) the samples, provides decoded data of user terminal 120 to data sink 2058, and provides control data and scheduling information to the controller / To the processor 2060.

  On the uplink, at terminal 120x, TX data processor 2072 receives traffic data from data source 2070 and control data (eg, Ack) from controller / processor 2060. A TX data processor 2072 processes traffic data and control data based on the rate selected for the terminal and generates data chips. Transmitter 2074 processes the data chips and generates an uplink signal that is transmitted from antenna 2052 to access point 110.

  In access point 110, antenna 2016 receives an uplink signal from the terminal. Receiver 2030 processes the received signal from antenna 2016 and provides samples. RX data processor 2032 processes the samples and provides decoded data for each terminal to data sink 2034 and provides control data to controller / processor 2020.

  Controllers / processors 2020 and 2060 direct the operation at access point 110 and terminal 120x, respectively. The scheduler 2024 performs terminal scheduling based on any of the above embodiments. The scheduler 2024 may be provided in the access point shown in FIG. 20, or another network entity.

  The scheduling and transmission techniques described herein may be implemented by various means. For example, these techniques may be implemented in hardware, firmware, software, or a combination thereof. For hardware implementation, an access point or terminal processing unit may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), Implemented in a field programmable gate array (FPGA), processor, controller, microcontroller, microprocessor, electronic device, other electronic unit designed to perform the functions described herein, or combinations thereof Also good.

  For firmware and / or software implementations, the technology may be implemented by modules (eg, procedures, functions, etc.) that perform the functions described herein. Firmware and / or software code may be stored in a memory (eg, memory 2022 or 2062 of FIG. 20) and executed by a processor (eg, processor 2020 or 2060). The memory may be configured within the processor or external to the processor.

  The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. . Accordingly, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. . Accordingly, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
The invention described in the scope of claims at the beginning of the filing of the present application will be appended.
[1]
Scheduling the first station in a first period having a first period, a first start time, and a first end time;
At least one processor configured to schedule a second station in a second period having a second period and a second start time prior to the first end time;
And a memory coupled to the at least one processor.
[2]
The at least one processor comprises:
[1] configured to schedule a third station in a third period having a third period and a third start time prior to a second end time of the second period apparatus.
[3]
The at least one processor comprises:
Sending a first transmission to the first station during the first period;
Sending an indication of the completion of the first transmission before the first end time;
The apparatus of [1] configured to send a second transmission to the second station before the first end time in the second period.
[4]
The at least one processor comprises:
The apparatus according to [3], configured to perform channel access before the first transmission.
[5]
The at least one processor comprises:
The apparatus according to [3], configured to send the first transmission without performing channel access.
[6]
The first period comprises a first part of an initial transmission of the first station and a second part of an additional transmission or retransmission of the first station, the second start time Is the end of the first part [1].
The first part covers a first data frame to the first station, a second data frame from the first station, and an acknowledgment for the second data frame [] Equipment.
[7]
The apparatus of [1], wherein the first period is approximately equal to a period of two data frames of each of a downlink and an uplink.
[8]
The apparatus of [1], wherein the first and second periods cover the same number of data frames.
[9]
The apparatus of [1], wherein the first and second periods are equal.
[10]
The apparatus according to [1], wherein the second start time is approximately halfway between the first start time and the first end time.
[11]
The first period covers a first set of transmission slots and the second period covers a second set of transmission slots including at least one transmission slot of the first set. [1] device.
[12]
[1] The apparatus according to [1], wherein the first and second periods are repeated at predetermined intervals.
[13]
The apparatus according to [12], wherein the predetermined interval is in a range of 10 to 20 milliseconds.
[14]
The at least one processor comprises:
[1] The apparatus of [1] configured to send a beacon for the first and second periods of the first and second stations.
[15]
The at least one processor comprises:
[1] The apparatus of [1] configured to send a multi-pole frame for the first and second periods of the first and second stations.
[16]
The first period is fixed in the first call period of the first station, and the second period is fixed in the second call period of the second station [1] Equipment.
[17]
The at least one processor comprises:
[1] The apparatus of [1] configured to set a transmission right (TXOP) restriction for one data frame for each channel access of a station in the access class.
[18]
The apparatus according to [1], wherein the first and second stations are IEEE 802.11 wireless local area network (WLAN) terminals.
[19]
[1] The apparatus according to [1], wherein the first and second periods are for transmission of voice over internet protocol (VoIP) data.
[20]
Scheduling the first station in a first period having a first period, a first start time, and a first end time;
Scheduling a second station in a second period having a second period and a second start time prior to the first end time.
[21]
Sending a first transmission to the first station during the first period;
Sending an indication of completion of the first transmission before the first end time;
Sending the second transmission to the second station during the second period and prior to the first end time [20].
[22]
The first period comprises a first part of an initial transmission of the first station and a second part of an additional transmission or retransmission of the first station, the second start time Is the end of the first part [20].
[23]
[20] The method of [20], further comprising the step of sending signaling of the first and second periods to the first and second stations.
[24]
Means for scheduling the first station in a first period having a first period, a first start time, and a first end time;
Means for scheduling a second station in a second period having a second period and a second start time prior to the first end time.
[25]
Means for sending a first transmission to the first station during the first period;
Means for sending an indication of completion of the first transmission before the first end time;
[24] The apparatus according to [24], further comprising means for sending a second transmission to the second station before the first end time in the second period.
[26]
[24] The apparatus of [24], further comprising means for sending the first and second period signaling to the first and second stations.
[27]
Scheduling the first station in a first period having a first period, a first start time, and a first end time;
A processor readable storing instructions executable in the device to schedule a second station in a second period having a second period and a second start time prior to the first end time Medium.
[28]
Sending a first transmission to the first station during the first period;
Sending an indication of the completion of the first transmission before the first end time;
[27] The processor-readable medium of [27], further storing instructions executable to send a second transmission to the second station prior to the first end time in the second period.
[29]
[27] The processor-readable medium of [27], further storing instructions executable to send the first and second periods of signaling to the first and second stations.
[30]
Schedule at least two stations with a specific traffic type in the entire service period;
At least one processor configured to serve each of the at least two stations in each one of at least two service periods within the total service period;
And a memory coupled to the at least one processor.
[31]
In order to serve a station, the at least one processor is
Send at least one frame to the station,
Receiving at least one frame from the station;
[30] The apparatus of [30] configured to send an indication of completion of the service period to the station.
[32]
The apparatus of [30], wherein the at least two service periods start at the beginning of the full service period.
[33]
[30] The apparatus of [30], wherein the at least two service periods start at different times.
[34]
[30] The apparatus of [30], wherein the at least two service periods end at different times.
[35]
The at least one processor comprises:
[30] The apparatus of [30], configured to send signaling of the at least two service periods to the at least two stations.
[36]
The at least one processor comprises:
[30] The apparatus of [30], wherein the apparatus is configured to send a multi-pol frame for the at least two service periods to the at least two stations.
[37]
The at least one processor comprises:
[30] The apparatus of [30], configured to send a beacon for the at least two service periods.
[38]
The at least one processor comprises:
[30] The apparatus of [30], configured to schedule the at least two stations in an order determined based on available power, link quality, amount of data to be exchanged, or a combination thereof.
[39]
The at least one processor comprises:
[30] The apparatus of [30], configured to determine a period of the service period of each station based on an estimate of a rate supported by the station and an amount of data exchanged with the station.
[40]
[30] The apparatus according to [30], wherein the entire service cycle is repeated at predetermined intervals.
[41]
The device according to [30], wherein the specific traffic type is Voice over Internet Protocol (VoIP).
[42]
Scheduling at least two stations having a particular traffic type in the entire service period;
Servicing each of the at least two stations in each one of at least two service periods within the full service period.
[43]
Servicing each of the at least two stations comprises:
Sending at least one frame to the station;
Receiving at least one frame from the station;
Sending the indication of completion of the service period to the station. [42].
[44]
[42] The method of [42], further comprising sending the signaling of the at least two service periods to the at least two stations.
[45]
Means for scheduling at least two stations having a particular traffic type during the entire service period;
Means for servicing each of the at least two stations in each one of at least two service periods within the total service period.
[46]
Means for servicing each of the at least two stations;
Means for sending at least one frame to the station;
Means for receiving at least one frame from said station;
Means for sending an indication of completion of the service period to the station.
[47]
[45] The apparatus of [45], further comprising means for sending signaling of the at least two service periods to the at least two stations.
[48]
Schedule at least two stations with a specific traffic type in the entire service period;
A processor readable medium storing instructions operable to instruct the processor to service each of the at least two stations in each one of at least two service periods within the entire service period.
[49]
Send at least one frame to the station,
Receiving at least one frame from the station;
[48] The processor-readable medium of [48], further storing instructions executable to send an indication of completion of the service period to the station.
[50]
[48] The processor-readable medium of [48], further storing instructions executable to send signaling of the at least two service periods to the at least two stations.
[51]
An apparatus for a first station in a wireless network,
Receiving a first period of signaling in which the first station can receive transmissions, overlapping a second period in which the second station can receive transmissions; And
At least one processor configured to monitor transmissions to the first station during the first period;
And a memory coupled to the at least one processor.
[52]
The at least one processor comprises:
Receiving at least one frame sent to the first station;
Sending at least one frame from the first station;
[51] The apparatus of [51] configured to receive an indication of completion of the transmission to the first station.
[53]
The at least one processor comprises:
Receiving an indication of completion of the transmission to the first station;
[51] The apparatus of [51] configured to transition to a power saving mode, potentially before the end of the first period upon receipt of the indication.
[54]
The apparatus of [51], wherein the first period covers two data frames from the first station.
[55]
[54] The apparatus of [54], wherein the first period overlaps the second period for one of the two data frames.
[56]
The at least one processor comprises:
[51] The apparatus of [51], configured to receive a multi-pole frame together with the signaling of the first period.
[57]
The at least one processor comprises:
[51] The apparatus according to [51], wherein the apparatus is configured to determine whether to power-cut the reception chain based on a time length from reception of the signaling to start of the first period.
[58]
The at least one processor comprises:
Establish a call,
[51] The apparatus of [51], configured to receive the signaling for the first period and an interval at which the first period is repeated.
[59]
[51] The apparatus of [51], wherein the transmission of the first station is Voice over Internet Protocol (VoIP).
[60]
Receiving signaling of a first period in which a first station can receive transmissions, wherein the first period is a second period in which a second station can receive transmissions; Duplicate steps and
Monitoring transmissions to the first station during the first period.
[61]
Receiving at least one frame sent to the first station;
Sending at least one frame from the first station;
Receiving the indication of completion of the transmission to the first station. [60].
[62]
Receiving an indication of completion of the transmission to the first station;
[60] The method of [60], further comprising the step of transitioning to a power saving mode upon receipt of the indication, potentially before the end of the first period.
[63]
An apparatus for a first station in a wireless network,
Means for receiving signaling of a first period in which the first station can receive transmissions, wherein the first period is a second period in which the second station can receive transmissions; Overlapping with means, and
Means for monitoring transmissions to the first station during the first period.
[64]
Means for receiving at least one frame sent to the first station;
Means for sending at least one frame from the first station;
[63] The apparatus of [63], further comprising means for receiving an indication of completion of the transmission to the first station.
[65]
Means for receiving an indication of completion of the transmission to the first station;
[63] The apparatus of [63], further comprising means for transitioning to a power saving mode, potentially upon receipt of the indication, prior to the end of the first period.

Claims (65)

Scheduling the first station in a first period having a first period, a first start time, and a first end time;
At least one processor configured to schedule a second station in a second period having a second period and a second start time prior to the first end time;
And a memory coupled to the at least one processor. The at least one processor comprises:
2. The third station is configured to schedule a third station in a third period having a third period and a third start time prior to a second end time of the second period. The device described. The at least one processor comprises:
Sending a first transmission to the first station during the first period;
Sending an indication of the completion of the first transmission before the first end time;
The apparatus of claim 1, configured to send a second transmission to the second station prior to the first end time in the second period. The at least one processor comprises:
The apparatus of claim 3, wherein the apparatus is configured to perform channel access prior to the first transmission. The at least one processor comprises:
The apparatus of claim 3, configured to send the first transmission without performing channel access. The first period comprises a first part of an initial transmission of the first station and a second part of an additional transmission or retransmission of the first station, the second start time The apparatus of claim 1, wherein is the end of the first portion.
The first portion covers a first data frame to the first station, a second data frame from the first station, and an acknowledgment for the second data frame. The device described in 1.   The apparatus of claim 1, wherein the first period is approximately equal to a period of two data frames each of a downlink and an uplink.   The apparatus of claim 1, wherein the first and second periods cover the same number of data frames.   The apparatus of claim 1, wherein the first and second time periods are equal.   The apparatus of claim 1, wherein the second start time is approximately halfway between the first start time and the first end time.   The first period covers a first set of transmission slots and the second period covers a second set of transmission slots including at least one transmission slot of the first set. The apparatus of claim 1.   The apparatus of claim 1, wherein the first and second periods are repeated at predetermined intervals.   The apparatus of claim 12, wherein the predetermined interval is in a range of 10 to 20 milliseconds. The at least one processor comprises:
The apparatus of claim 1, configured to send beacons for the first and second periods of the first and second stations. The at least one processor comprises:
The apparatus of claim 1, configured to send a multi-pole frame for the first and second periods of the first and second stations.   The first period is fixed in a first call period of the first station, and the second period is fixed in a second call period of the second station. The device described in 1. The at least one processor comprises:
The apparatus of claim 1, wherein the apparatus is configured to set a transmission right (TXOP) limit of one data frame for each channel access of a station in an access class.   2. The apparatus of claim 1, wherein the first and second stations are IEEE 802.11 wireless local area network (WLAN) terminals.   The apparatus of claim 1, wherein the first and second periods are for transmission of Voice over Internet Protocol (VoIP) data. Scheduling the first station in a first period having a first period, a first start time, and a first end time;
Scheduling a second station in a second period having a second period and a second start time prior to the first end time. Sending a first transmission to the first station during the first period;
Sending an indication of completion of the first transmission before the first end time;
21. The method of claim 20, further comprising: sending a second transmission to the second station before the first end time in the second period.   The first period comprises a first part of an initial transmission of the first station and a second part of an additional transmission or retransmission of the first station, the second start time 21. The method of claim 20, wherein is the end of the first portion.   21. The method of claim 20, further comprising sending the first and second period signaling to the first and second stations. Means for scheduling the first station in a first period having a first period, a first start time, and a first end time;
Means for scheduling a second station in a second period having a second period and a second start time prior to the first end time. Means for sending a first transmission to the first station during the first period;
Means for sending an indication of completion of the first transmission before the first end time;
25. The apparatus of claim 24, further comprising means for sending a second transmission to the second station prior to the first end time during the second period.   25. The apparatus of claim 24, further comprising means for sending the first and second period signaling to the first and second stations. Scheduling the first station in a first period having a first period, a first start time, and a first end time;
A processor readable storing instructions executable in the device to schedule a second station in a second period having a second period and a second start time prior to the first end time Medium. Sending a first transmission to the first station during the first period;
Sending an indication of the completion of the first transmission before the first end time;
28. The processor-readable medium of claim 27, further storing instructions executable in the second period to send a second transmission to the second station prior to the first end time. .   28. The processor-readable medium of claim 27, further storing instructions executable to send the first and second periods of signaling to the first and second stations. Schedule at least two stations with a specific traffic type in the entire service period;
At least one processor configured to serve each of the at least two stations in each one of at least two service periods within the total service period;
And a memory coupled to the at least one processor. In order to serve a station, the at least one processor is
Send at least one frame to the station,
Receiving at least one frame from the station;
32. The apparatus of claim 30, configured to send an indication of completion of the service period to the station.   31. The apparatus of claim 30, wherein the at least two service periods start at the beginning of the full service period.   The apparatus of claim 30, wherein the at least two service periods start at different times.   The apparatus of claim 30, wherein the at least two service periods end at different times. The at least one processor comprises:
32. The apparatus of claim 30, wherein the apparatus is configured to send signaling of the at least two service periods to the at least two stations. The at least one processor comprises:
31. The apparatus of claim 30, configured to send a multi-pol frame for the at least two service periods to the at least two stations. The at least one processor comprises:
32. The apparatus of claim 30, configured to send a beacon for the at least two service periods. The at least one processor comprises:
31. The apparatus of claim 30, configured to schedule the at least two stations in an order determined based on available power, link quality, amount of data to exchange, or a combination thereof. The at least one processor comprises:
31. The apparatus of claim 30, configured to determine a duration of the service period for each station based on an estimate of a rate supported by the station and the amount of data exchanged with the station.   The apparatus of claim 30, wherein the full service period is repeated at predetermined intervals.   The apparatus of claim 30, wherein the specific traffic type is Voice over Internet Protocol (VoIP). Scheduling at least two stations having a particular traffic type in the entire service period;
Servicing each of the at least two stations in each one of at least two service periods within the full service period. Servicing each of the at least two stations comprises:
Sending at least one frame to the station;
Receiving at least one frame from the station;
43. The method of claim 42, further comprising sending an indication of completion of the service period to the station.   43. The method of claim 42, further comprising sending signaling of the at least two service periods to the at least two stations. Means for scheduling at least two stations having a particular traffic type during the entire service period;
Means for servicing each of the at least two stations in each one of at least two service periods within the total service period. Means for servicing each of the at least two stations;
Means for sending at least one frame to the station;
Means for receiving at least one frame from said station;
46. The apparatus of claim 45, comprising means for sending an indication of completion of the service period to the station.   46. The apparatus of claim 45, further comprising means for sending signaling of the at least two service periods to the at least two stations. Schedule at least two stations with a specific traffic type in the entire service period;
A processor readable medium storing instructions operable to instruct the processor to service each of the at least two stations in each one of at least two service periods within the entire service period. Send at least one frame to the station,
Receiving at least one frame from the station;
49. The processor-readable medium of claim 48, further storing instructions executable to send an indication of completion of the service period to the station.   49. The processor-readable medium of claim 48, further storing instructions executable to send signaling of the at least two service periods to the at least two stations. An apparatus for a first station in a wireless network,
Receiving a first period of signaling in which the first station can receive transmissions, overlapping a second period in which the second station can receive transmissions; And
At least one processor configured to monitor transmissions to the first station during the first period;
And a memory coupled to the at least one processor. The at least one processor comprises:
Receiving at least one frame sent to the first station;
Sending at least one frame from the first station;
52. The apparatus of claim 51, configured to receive an indication of completion of the transmission to the first station. The at least one processor comprises:
Receiving an indication of completion of the transmission to the first station;
52. The apparatus of claim 51, wherein upon receiving the indication, the apparatus is configured to transition to a power saving mode potentially before the end of the first period.   52. The apparatus of claim 51, wherein the first period covers two data frames from the first station.   55. The apparatus of claim 54, wherein the first period overlaps with the second period for one of the two data frames. The at least one processor comprises:
52. The apparatus of claim 51, configured to receive a multi-pole frame with the signaling of the first period. The at least one processor comprises:
52. The apparatus of claim 51, configured to determine whether to power down a receive chain based on a time length from receipt of the signaling to the start of the first period. The at least one processor comprises:
Establish a call,
52. The apparatus of claim 51, configured to receive the signaling for the first period and an interval at which the first period is repeated.   52. The apparatus of claim 51, wherein the transmission of the first station is Voice over Internet Protocol (VoIP). Receiving signaling of a first period in which a first station can receive transmissions, wherein the first period is a second period in which a second station can receive transmissions; Duplicate steps and
Monitoring transmissions to the first station during the first period. Receiving at least one frame sent to the first station;
Sending at least one frame from the first station;
61. The method of claim 60, further comprising receiving an indication of completion of the transmission to the first station. Receiving an indication of completion of the transmission to the first station;
61. The method of claim 60, further comprising: upon receiving the indication, transitioning to a power saving mode, potentially before the end of the first period. An apparatus for a first station in a wireless network,
Means for receiving signaling of a first period in which the first station can receive transmissions, wherein the first period is a second period in which the second station can receive transmissions; Overlapping with means, and
Means for monitoring transmissions to the first station during the first period. Means for receiving at least one frame sent to the first station;
Means for sending at least one frame from the first station;
64. The apparatus of claim 63, further comprising means for receiving an indication of completion of the transmission to the first station. Means for receiving an indication of completion of the transmission to the first station;
64. The apparatus of claim 63, further comprising means for transitioning to a power saving mode upon receipt of the indication, potentially before the end of the first period.

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